The flat panel display devices possess many merits of thin frame, power saving, no radiation, etc. and have been widely used. Present flat panel display devices mainly comprise a LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Display).
Thin Film transistors (TFT) are important components of a flat panel display The TFTs can be formed on a glass substrate and a plastic substrate and generally employed as switch elements and driving elements utilized in the flat panel display devices, such as LCDs, OLEDs and et cetera.
The oxide semiconductor TFT technology is the most popular skill at present. The oxide semiconductor has higher electron mobility. In comparison with the Low Temperature Poly-silicon (LTPS), the oxide semiconductor manufacture process is simpler and possesses higher compatibility with the amorphous silicon process. It can be applicable to the skill fields of Liquid Crystal Display, Organic Light Emitting Display, Flexible Display and etc. Because it fits the new generation production lines and has possible applications for displays with Large, Middle and Small sizes. The oxide semiconductor has the great opportunity of application development.
The oxide semiconductor TFT substrate structure with more development at present is the etch-stopper layer (ESL) structure. FIG. 1 to FIG. 5 sequentially shows the process flows of the common manufacture method of the oxide semiconductor TFT substrate: first, deposing a first metal layer on a substrate 100, and implementing pattern process to the first metal layer with a first mask to form a bottom gate 200; second, deposing a gate isolation layer 300; third, deposing an oxide semiconductor film, and implementing pattern process to the oxide semiconductor film with a second mask to form a oxide semiconductor layer 400; fourth, deposing an etch-stopper layer 500, and implementing pattern process to the etch-stopper layer 500 with a third mask; fifth, deposing a second metal layer, and implementing pattern process to the second metal layer with a fourth mask to form a source/a drain 600.
Several following issues exist in the aforesaid common manufacture method of the oxide semiconductor TFT substrate: A. except the substrate 100, the other layers respectively requires one mask for one complete photolithographic process (including processes of photo, etching, stripping and etc.) for implementing pattern process, and the necessary amount of the masks are more, and the process flow is longer, and the production efficiency is lower and the production cost is higher; B. the interfaces of the oxide semiconductor layer 400, the gate isolation layer 300 and the etch-stopper layer 500 can be easily contaminated with the etchant, stripper, and the risk of the TFT performance degradation exist; C. the contact area of the source/the drain 600 with the oxide semiconductor layer 400 is smaller, and the contact resistance is larger, and the on state current of the TFT is lower.